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Soluble Polymer Allows Writing in Liquid with Light

Researchers from the Laboratory of Polymer Chemistry in the University of Helsinki’s Department of Chemistry in Finland have managed to draw in an alcohol-based solution using laser light. The research was published in the journal, Macromolecules.

The scientists manufactured photochemically active polymers that can be dissolved in water or certain alcohols. In the study, a 365-nm laser was aimed at a solution into which the polymer was partially dissolved. When exposed to light, the polymer switched to its cis conformation, dissolving completely and leaving a clear form that was visible in the cloudy solution.

The polymer chain includes azo compounds, which can be switched from atrans conformation to a cis conformation using light. As the two conformations are different in solubility, a ray of light can “draw” in an ethanol-based dispersion of the polymer. The switch from trans to cis happens in the entire polymer chain.

This effect where light causes the polymer to dissolve completely and be made visible can last several hours depending, for example, on the concentration of the solution. Previously, the researchers say, drawing in liquid had been impossible.

This discovery is particularly significant for the development of new materials for optics and electronics. 

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